At present, in accordance with the prior art and for particular commercial requirements, three different types of caps suitable for prize competitions are used.
The first type consists of a cap in the form of a metallic shell, the internal side having a bottom upon which an opaque PVC seal is applied after treatment with adhesive paint. Given its affinity with the paint, the said seal is easily detached, so that an inscription present on the bottom of the cap can be read.
The second type of cap, again having an opaque PVC seal, differs from the first in that the inscription is made in such a way that it is transferred from the shell to the seal itself: therefore, this type of cap is ideal for use when the seal must be used as proof of a win, since it is easier to send a seal rather than the entire cap.
The third type of cap has a transparent seal (PVC or PVC--free) which cannot be detached from the bottom of the cap. There is an inscription on the bottom of the cap itself, clearly visible through the seal. However, this cap is impractical for use in prize competitions, since the entire cap is required as proof of a win, being less convenient than the second type of cap, since, as already indicated, it is easier to post a seal than a cap. A further disadvantage of this third type of cap is that a sufficiently opaque bottle is required, to prevent the inscription being read from the outside of the bottle.
None of the three types of PVC-based crown caps made according to the prior art can be marketed in those states in which the law forbids the use of PVC crown caps.
To comply with such regulations and requirements and, at the same time, obtain a cap which has an easily detachable PVC--free seal, a new technology designed to control the adhesion of the PVC--free material to the cap is needed.